Fresh air plenum module for a fan coil unit

ABSTRACT

A fresh air plenum module ( 10 ) for attachment to a fan coil unit ( 12 ) for introducing air from an outdoor setting, wherein the fresh air plenum module includes: a first inlet ( 14 ) for connection to an outlet ( 24 ) of the fan coil unit; a second inlet ( 16 ) for connection to an air handling unit; an outlet ( 18 ) for discharge of the outdoor air and the conditioned air; and a merging volume ( 20 ) in communication with the first inlet, the second inlet and the outlet; in use, a flow of the outdoor air from the second inlet through the merging volume to the outlet generates a pressure gradient which induces a flow of air through the first inlet and into the fresh air plenum module from the fan coil unit.

FOREIGN PRIORITY

This application claims priority to European Patent Application No.22156617.7, filed Feb. 14, 2022, and all the benefits accruing therefromunder 35 U.S.C. § 119, the contents of which in its entirety are hereinincorporated by reference.

TECHNICAL FIELD OF INVENTION

The present invention relates to a fresh air plenum module for theintroduction of fresh air into an indoor setting, where the fresh airplenum module is for fitting to a fan coil unit. It also relates to acorresponding method of operating a system comprising a fan coil unitfitted with a fresh air plenum module.

BACKGROUND OF THE INVENTION

Conventionally, air handling units (AHUs) and the like are responsiblefor the distribution of fresh air within a commercial or industrialbuilding such as a hotel or office. For example, an AHU takes freshambient air from outside (e.g. outdoors) and distributes it to one ormore rooms inside of the building (e.g. indoors) via one or more ducts.One or more of these rooms may each comprise a fan coil unit (FCU)responsible for conditioning (e.g. heating and/or cooling) the air inits associated room.

A typical FCU comprises a heat exchanger coil and a fan. The coil isconfigured to receive hot or cold fluid from a central plant, and thefan is configured to blow or draw air from the room through the coil sothat heat can be exchanged between the air flow and the fluid in thecoil.

It would beneficial if the flow of fresh ambient air that is introducedinto a room of a building could be utilised to improve the efficiency ofoperation of a FCU located in said room.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a freshair plenum module for attachment to a fan coil unit for introducing airfrom an outdoor setting, wherein the fresh air plenum module comprises:a first inlet for connection to an outlet of the fan coil unit; a secondinlet for connection to an air handling unit; an outlet for discharge ofthe outdoor air and the conditioned air; and a merging volume incommunication with the first inlet, the second inlet and the outlet;wherein, in use, a flow of the outdoor air from the second inlet throughthe merging volume to the outlet generates a pressure gradient whichinduces a flow of conditioned air through the first inlet and into thefresh air plenum module from the fan coil unit.

With the above fresh air plenum module it is possible to easily modify apre-existing fan coil unit to add a fresh (outdoor) air injectioncapability where the injection of fresh air induces an increase in theflow of conditioned air through the fan coil unit. Thus, upon newinstallation or as a retrofit for previously installed fan coil units itbecomes possible to add in the proposed fresh air plenum module tothereby introduce a fresh air induction function to the system, whichimproves the efficiency of the operation of the fan coil unit (when thefan is operated) and also provides a new mode of operation of the fancoil unit (wherein the fan is not operated) which allows the system toprovide some air conditioning at a greatly reduced energy consumption.

The flow of outdoor air through the merging volume causes a drop instatic pressure in the merging volume. This decrease in pressure, e.g.generating a negative (gauge) pressure, in the merging volume relativeto the pressure in the fan coil unit causes air to be pulled passivelyfrom the fan coil unit, through the first inlet and into the fresh airplenum module. Thus, the flow of outdoor air through the merging volumeinduces an airflow through the fan coil unit.

The fresh air plenum module is considered to be a new air plenum module,in that it is configured/suitable for introducing new air into a fancoil unit system and/or its environment, the new air being fresh/outdoorair.

On the other hand, conditioned air is air from the environment (e.g.indoors, hotel room) that has passed through the coil of the fan coilunit (so that heat can be exchanged between the air flow and the fluidin the coil).

In some implementations the fresh air plenum module is advantageouslyconfigured to induce a flow of conditioned air through the fan coil unitat an air flow rate of between 20% and 300% of the air flow rate throughthe second inlet (e.g. the maximum air flow rate that can be generatedby an AHU).

The fresh air plenum module may comprise at least one nozzle fluidlyconnected to the second inlet for injecting the outdoor air into themerging volume.

The fresh air plenum module may comprise a first plenum compartmentconnected to the second inlet and configured to supply outdoor air to atleast one first nozzle; and a second plenum compartment connected to thesecond inlet and configured to supply outdoor air to at least one secondnozzle.

The first plenum compartment may be located on a first internal side ofthe fresh air plenum module; and the second plenum compartment may belocated on a second internal side of the fresh air plenum module;wherein the first internal side and the second internal side are in afacing spaced relationship.

The second inlet may be configured to divide the outdoor air flow fromthe air handling unit equally between the first plenum compartment andthe second plenum compartment.

The second inlet may be configured to direct more than half of theoutdoor airflow from the air handling unit to the first plenumcompartment.

The second inlet may be configured to direct more than half of theoutdoor airflow from the air handling unit to the second plenumcompartment.

A volume of the first plenum compartment may be the same as a volume ofthe second plenum compartment.

A volume of the first plenum compartment may be greater than a volume ofthe second plenum compartment.

A volume of the second plenum compartment may be greater than a volumeof the first plenum compartment.

A width of the or each first nozzle may be the same as a width of theoutlet.

A width of the or each second nozzle may be the same as a width of theoutlet.

The shape of the or each first nozzle may be rectangular orsemi-circular.

The shape of the or each second nozzle may be rectangular orsemi-circular.

The shape of the or each first nozzle and/or the shape of the or eachsecond nozzle may be configured to induce a flow of air at apredetermined air flow rate.

The shape of the or each first nozzle may be the same as the shape ofthe or each second nozzle.

The shape of the or each first nozzle may be different from the shape ofthe or each second nozzle.

The at least one first nozzle may be a first set of nozzles; and the atleast one second nozzle may be a second set of nozzles.

The first set of nozzles may comprise more nozzles than the second setof nozzles.

The second set of nozzles may comprise more nozzles than the first setof nozzles.

The first set of nozzles may comprise a plurality of nozzles distributedin a straight line facing the outlet.

The first set of nozzles may comprise a plurality of nozzles distributedin a plurality of straight lines facing the outlet.

Where the first set of nozzles is distributed in a plurality of straightlines, the nozzles in one line may be offset from the nozzles inadjacent line(s).

The second set of nozzles may comprise a plurality of nozzlesdistributed in a straight line facing the outlet.

The second set of nozzles may comprise a plurality of nozzlesdistributed in a plurality of straight lines facing the outlet.

Where the second set of nozzles is distributed in a plurality ofstraight lines, the nozzles in one line may be offset from the nozzlesin adjacent line(s).

The arrangement of the first set of nozzles and/or the arrangement ofthe second set of nozzles may be configured to suit the target FCU.

The arrangement of the first set of nozzles and/or the arrangement ofthe second set of nozzles may be configured to induce a flow of air at apredetermined air flow rate.

The arrangement of the first set of nozzles and/or the arrangement ofthe second set of nozzles may be configured to maintain a predeterminedpressure in the first plenum compartment and/or the second plenumcompartment, respectively.

The nozzle wall of the first plenum compartment may comprise a curvedportion.

The nozzle wall of the first plenum compartment may comprise a straightportion, and an angle between the straight portion and the firstinternal side of the fresh air plenum module is less than 60 degrees,preferably less than 30 degrees.

The nozzle wall of the second plenum compartment may comprise a curvedportion.

The nozzle wall of the second plenum compartment may comprise a straightportion, and an angle between the straight portion and the secondinternal side of the fresh air plenum module is less than 60 degrees,preferably less than 30 degrees.

According to a second aspect of the invention, there is provided asystem comprising the fresh air plenum module according to the firstaspect and a fan coil unit, wherein the first inlet of the fresh airplenum module is coupled to the outlet of the fan coil unit.

The system may comprise an air handling unit, wherein the second inletof the fresh air plenum module is connected to the outlet of the airhandling unit.

The fan coil unit may have a controller configured to independentlyoperate the coil of the fan coil unit and the fan of the fan coil unit.

The controller may be configured to operate the system in an inductionmode.

The induction mode may be defined in that: the coil of the fan coil unitis operated and the fan of the fan coil unit is not operated, andwherein the flow of conditioned air through the fan coil unit is inducedby the pressure gradient generated by the flow of outdoor air throughthe fresh air plenum module.

The controller may be configured to operate the system in a boost mode.

The boost mode may be defined in that: the coil of the fan coil unit isoperated and the fan of the fan coil unit is operated, and wherein theflow of conditioned air through the fan coil unit is provided by thepressure gradient generated by the flow of outdoor air through the freshair plenum module and the operation of the fan.

The controller may be configured to operate the system in an eco mode.

The eco mode may be defined in that: the coil of the fan coil unit isnot operated and the fan of the fan coil unit is not operated, andwherein the flow of outdoor air through the fresh air plenum modulegenerates a pressure gradient which induces a flow of air through thefan coil unit.

It is thus apparent that the ‘eco mode’ is a mode of operation whereinthe fan coil unit is turned off and/or consuming no (or at least low)power. Accordingly, ‘eco mode’ as used herein can also be taken to mean‘economy mode’, or ‘green mode’.

According to a third aspect, there is provided a method of installationof a fresh air plenum module or system according to the first or secondaspect, the method comprising: providing the fresh air plenum module;fitting the first inlet of the fresh air plenum module to the outlet ofa fan coil unit; and connecting the second inlet of the fresh air plenummodule to the outlet of an air handling system.

According to a fourth aspect, there is provided a method of operating asystem according to the second aspect, the method comprising operatingthe system in an induction mode, the induction mode comprising:providing outdoor air to the second inlet of the fresh air plenummodule; operating a coil of the fan coil unit; and not operating a fanof the fan coil unit; wherein the flow of conditioned air through thefan coil unit is induced by the pressure gradient generated by the flowof outdoor air through the fresh air plenum module.

The method may comprise operating the system in a boost mode, the boostmode comprising: providing outdoor air to the second inlet of the freshair plenum module; operating the coil of the fan coil unit; andoperating the fan of the fan coil unit; wherein the flow of conditionedair through the fan coil unit is provided by the pressure gradientgenerated by the flow of outdoor air through the fresh air plenum moduleand the operation of the fan.

The method may comprise operating the system in an eco mode, the ecomode comprising: providing outdoor air to the second inlet of the freshair plenum module; not operating a coil of the fan coil unit; and notoperating a fan of the fan coil unit; wherein the pressure gradientgenerated by the flow of outdoor air through the fresh air plenum moduleinduces a flow of air through the fan coil unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 shows a fresh air plenum module and a fan coil unit;

FIG. 2 shows the fresh air plenum module of FIG. 1 connected to the fancoil unit of FIG. 1 ;

FIG. 3 shows a cross-sectional side view of the system of FIG. 2 ;

FIG. 4 shows a cross-sectional front view of the fresh air plenum moduleof FIGS. 1 and 2 without the fan coil unit; and

FIG. 5 shows a perspective view of another fresh air plenum module.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a fresh air plenum module 10 and a fan coil unit 12, andFIGS. 2 and 3 show a system comprising the fresh air plenum module 10coupled to the fan coil unit 12. This connection can be done as amodification to a system with a pre-existing fan coil unit 12 to providean added air injection capability, or it can be done along withinstallation of the fan coil unit 12. The fresh air plenum module 10 isfor introducing a flow of fresh air from an outdoor setting to induce aflow of (conditioned) air through the fan coil unit which improves theefficiency of the operation of the fan coil unit (when the fan isoperated) and also provides a new mode of operation of the fan coil unit(wherein the fan is not operated), the new mode allowing the system toprovide a small amount of air conditioning at a greatly reduced energyconsumption.

The fresh air plenum module comprises a first inlet 14 for connection toan outlet 24 of the fan coil unit 12, a second inlet 16 for connectionto an air handling unit (not shown), an outlet 18 for discharge of theoutdoor air and the conditioned air, and a merging volume 20 incommunication with the first inlet 14, the second inlet 16 and theoutlet 18.

FIGS. 3 and 4 show further detail of the fan coil unit 12 and fresh airplenum module 10.

The fan coil unit 12 comprises an inlet 22, the outlet 24, a fan 26 anda heat exchanger coil 28. The coil 28 is configured to receive hot orcold fluid from a central source (not shown), and the fan 26 isconfigured to blow/draw air from the room through the coil 28 so thatheat can be exchanged between the air flow and the fluid in the coil 28.The fan coil unit 12 also comprises a controller (not shown) which isable to operate the fan 26 and the coil 28 separately and independentlyof each other.

In particular, the fresh air plenum module 10 comprises a first plenumcompartment 30 a and a second plenum compartment 30 b. The first plenumcompartment 30 a and the second plenum compartment 30 b are connected tothe second inlet 16 such that outdoor air is able to flow from thesecond inlet 16 into either the first plenum compartment 30 a and thesecond plenum compartment 30 b.

In this example, the first plenum compartment 30 a is located on a firstinternal side of the fresh air plenum module 10, the first internal sidebeing a top side of the fresh air plenum module 10. The second plenumcompartment 30 b is located on a second internal side of the fresh airplenum module 10, the second internal side being a bottom side of thefresh air plenum module 10. Accordingly, the first internal side and thesecond internal side are in a facing spaced relationship. The firstplenum compartment 30 a and second plenum compartment 30 b extend alongthe whole width of the first internal side and the second internal siderespectively.

In this example, the volume of the first plenum compartment 30 a is thesame as the volume of the second plenum compartment 30 b. However, thevolume of the first plenum compartment 30 a may be greater than thevolume of the second plenum compartment 30 b or the volume of the secondplenum compartment 30 b may be greater than the volume of the firstplenum compartment 30 a.

The fresh air plenum module 10 comprises an air divider 32 configured todistribute the outdoor air flow from the second inlet 16 between thefirst plenum compartment 30 a and the second plenum compartment 30 b. Inthis example the air divider 32 is configured to distribute the outdoorair flow from the second inlet 16 equally between the first plenumcompartment 30 a and the second plenum compartment 30 b, but the airdivider 32 may be configured to distribute the outdoor air flow from thesecond inlet 16 unequally between the first plenum compartment 30 a andthe second plenum compartment 30 b depending on the requirements of theenvironment.

The first plenum compartment 30 a is configured to supply the outdoorair to a first set 34 a of one or more nozzles 34, and the second plenumcompartment 30 b is configured to supply the outdoor air to a second set34 b of one or more nozzles 34.

Each nozzle 34 is configured to inject the outdoor air into the mergingvolume 20 of the fresh air plenum module 10. As such, each nozzle 34 maybe shaped in order to provide a high-velocity injection of outdoor airinto the merging volume 20. Each nozzle 34 is facing/directed towardsthe outlet 18.

The first set of nozzles 34 a and the second set of nozzles 34 b areconfigured to provide air injection flow characteristics depending onthe requirements of the system/environment.

In the exemplary fresh air plenum 10 of FIGS. 1-4 , the first set ofnozzles 34 a comprises the same number of nozzles 34 as the second setof nozzles 34 b; however, the first set of nozzles 34 a may comprisemore nozzles 34 than the second set of nozzles 34 b, or the second setof nozzles 34 b may comprise more nozzles 34 than the first set ofnozzles 34 a.

The first set of nozzles 34 a is distributed on a nozzle wall of thefirst plenum compartment 30 a. The first set of nozzles 34 a comprisesfour rows of nozzles 34, each row comprising a straight line of nozzles34 facing towards the outlet 18. Each row of nozzles 34 is offset fromthe rows of nozzles adjacent to it, to form a “staggered” arrangement.

The second set of nozzles 34 b is distributed on a nozzle wall of thesecond plenum compartment 30 b. In this example, the second set ofnozzles 34 b is arranged in the same way as the first set of nozzles 34a.

In this example, as shown in FIG. 3 , the nozzle wall of the firstplenum compartment 30 a and the nozzle wall of the second plenumcompartment 30 b each comprise a curved portion on which the nozzles 34are distributed. The curved portions are secured to the first internalside and second internal side respectively.

FIG. 5 shows another example of a fresh air plenum 100. The fresh airplenum 100 is similar to the fresh air plenum 10 except in that it hasdifferently shaped plenum compartments 30 a, 30 b and different nozzle34 arrangements.

For example, the nozzle wall of the first plenum compartment 30 a andthe nozzle wall of the second plenum compartment 30 b each comprise astraight portion. The straight portion of the nozzle wall of the firstplenum compartment 30 a is angled at 60 degrees from the first internalside of the fresh air plenum module 100. The straight portion of thenozzle wall of the second plenum compartment 30 b is angled at 60degrees from the second internal side of the fresh air plenum module100.

The nozzle wall of each plenum compartment 30 a, 30 b further comprisesa curved portion that protrudes into the merging volume 20 and a secondstraight portion which joins the curved portion to an edge of the outlet18. Thus, it can be seen that the volume of the plenum compartments 30a, 30 b of the fresh air plenum module 100 is greater than the volume ofthe plenum compartments 30 a, 30 b of the fresh air plenum module 10.

The first set of nozzles 34 a is distributed on the nozzle wall of thefirst plenum compartment 30 a. The first set of nozzles 34 a comprisesfour nozzles 34 spaced apart from each other, each facing towards theoutlet 18. Each nozzle 34 is rectangular in shape, and extends acrossthe full width of the outlet 18.

The second set of nozzles 34 b is distributed on a nozzle wall of thesecond plenum compartment 30 b in the same way as the first set ofnozzles 34 a.

In both of the examples above, the first plenum compartment 30 a is thesame as the second plenum compartment 30 b. Particularly, the second setof nozzles 34 b is arranged in the same way as the first set of nozzles34 a. However, the nozzle wall and arrangement of the second set ofnozzles 34 of the second plenum compartment 30 b may be different fromfirst plenum compartment 30 a, depending on the situation.

In other words, the shape, number and arrangement of the nozzles of thefirst set of nozzles 34 a and/or the nozzles of the second set ofnozzles 34 b may be selected to adapt the air flow to differing types offan coil unit and/or for different shapes of interior/housing of theplenum module 10, 100.

The fresh air plenum module 10, 100 can be fitted to the fan coil unit12 prior to installation of the system or can be retrofitted to apre-installed fan coil unit 12.

In order to connect the fresh air plenum module 10, 100 to the fan coilunit 12, the first inlet 14 is fitted to the outlet 24 of the fan coilunit 12. The second inlet 16 of the fresh air plenum module 10, 100 isfluidly connected (e.g. by a tube or pipe network) to the outlet of anair handling system (not shown).

In use, the system comprising the fresh air plenum module 10, 100 andthe fan coil unit 12 can be operated in one of an induction mode, aboost mode, and an eco mode.

In the induction mode of operation, fresh/outdoor air is provided to thesecond inlet 16 of the fresh air plenum module 10, 100, the coil 28 ofthe fan coil unit 12 is operated (to condition the air by heating orcooling) and the fan 26 of the fan coil unit 12 is not operated. Theflow of fresh/outdoor air from the second inlet 16, through the mergingvolume 20 and out of the outlet 18 causes a drop in pressure in themerging volume 20. This negative (gauge) pressure in the merging volume20 pulls air passively from the fan coil unit 12 through the first inlet14 and into the fresh air plenum module 10, 100. Thus, the flow offresh/outdoor air through the fresh air plenum module 10, 100 induces aflow of air through the fan coil unit 12 and the fresh air plenum module10, 100, this flow of air being conditioned by the coil 28 as it passesthrough it.

The induction mode of the system is therefore able to provide fresh aircirculation and conditioning functionality without requiring the fan 26to be operated, reducing the energy consumption required for thisfunctionality in comparison to present air conditioning systems.

In the boost mode of operation, fresh/outdoor air is provided to thesecond inlet 16 of the fresh air plenum module 10, 100, the coil 28 ofthe fan coil unit 12 is operated (to condition the air by heating orcooling) and the fan 26 of the fan coil unit 12 is operated to draw airthrough the fan coil unit 12 and fresh air plenum module 10, 100.

In this mode, the flow of fresh/outdoor air through the fresh air plenummodule 10, 100 still induces a flow of air through the fan coil unit 12and the fresh air plenum module 10, 100, therefore increasing theoverall volume of air flow through the system and increasing theefficiency of operation of the system in comparison to present airconditioning systems.

In the eco mode of operation, fresh/outdoor air is provided to thesecond inlet 16 of the fresh air plenum module 10, 100, and the coil 28and the fan 26 of the fan coil unit 12 are not operated. Again, the flowof fresh/outdoor air through the fresh air plenum module 10 in this modestill induces a flow of air through the fan coil unit 12 and the freshair plenum module 10, 100, even when air conditioning functionality isnot required.

The induction of a flow of air through the coil 28 of the fan coil unit12 even when air conditioning functionality is not required can preventdust from building up on the coil 28 and/or improve the air change rateof the room/system, without requiring the fan 26 to be operated (and,for example, consuming energy unnecessarily).

What is claimed is:
 1. A fresh air plenum module for attachment to a fancoil unit for introducing air from an outdoor setting, wherein the freshair plenum module comprises: a first inlet for connection to an outletof the fan coil unit; a second inlet for connection to an air handlingunit; an outlet for discharge of the outdoor air and the conditionedair; and a merging volume in communication with the first inlet, thesecond inlet and the outlet; wherein, in use, a flow of the outdoor airfrom the second inlet through the merging volume to the outlet generatesa pressure gradient which induces a flow of air through the first inletand into the fresh air plenum module from the fan coil unit.
 2. A freshair plenum module as claimed in claim 1, wherein the fresh air plenummodule comprises at least one nozzle fluidly connected to the secondinlet for injecting the outdoor air into the merging volume.
 3. A freshair plenum module as claimed in claim 2, wherein the fresh air plenummodule comprises a first plenum compartment connected to the secondinlet and configured to supply outdoor air to a first set of one or morenozzles; and a second plenum compartment connected to the second inletand configured to supply outdoor air to a second set of one or morenozzles.
 4. A fresh air plenum module as claimed in claim 3, wherein thefirst plenum compartment is located on a first internal side of thefresh air plenum module; and the second plenum compartment is located ona second internal side of the fresh air plenum module; wherein the firstinternal side and the second internal side are in a facing spacedrelationship.
 5. A fresh air plenum module as claimed in claim 3,wherein the second inlet is configured to divide the outdoor air flowfrom the air handling unit equally between the first plenum compartmentand the second plenum compartment.
 6. A fresh air plenum module asclaimed in claim 3, wherein the fresh air plenum module is configured todirect more than half of the outdoor airflow from the air handling unitto the first plenum compartment; or the fresh air plenum module isconfigured to direct more than half of the outdoor airflow from the airhandling unit to the second plenum compartment.
 7. A fresh air plenummodule as claimed in claim 3, wherein a volume of the first plenumcompartment is greater than a volume of the second plenum compartment;or the volume of the second plenum compartment is greater than thevolume of the first plenum compartment.
 8. A fresh air plenum module asclaimed in claim 3, wherein the first set of nozzles comprises morenozzles than the second set of nozzles; or wherein the second set ofnozzles comprises more nozzles than the first set of nozzles.
 9. Asystem comprising the fresh air plenum module of claim 1 and a fan coilunit, wherein the first inlet of the fresh air plenum module is coupledto the outlet of the fan coil unit.
 10. A system as claimed in claim 9,comprising an air handling unit, wherein the second inlet of the freshair plenum module is connected to the outlet of the air handling unit.11. A system as claimed in claim 9, wherein the fan coil unit has acontroller configured to independently operate the coil of the fan coilunit and the fan of the fan coil unit.
 12. A method of installation of afresh air plenum module or system as claimed in claim 1, the methodcomprising: providing the fresh air plenum module; fitting the firstinlet of the fresh air plenum module to the outlet of a fan coil unit;and connecting the second inlet of the fresh air plenum module to theoutlet of an air handling system.
 13. A method of operating a system asclaimed in claim 9, the method comprising operating the system in aninduction mode, the induction mode comprising: providing outdoor air tothe second inlet of the fresh air plenum module; operating a coil of thefan coil unit; and not operating a fan of the fan coil unit; wherein theflow of conditioned air through the fan coil unit is induced by thepressure gradient generated by the flow of outdoor air through the freshair plenum module.
 14. A method as claimed in claim 13, the methodcomprising operating the system in a boost mode, the boost modecomprising: providing outdoor air to the second inlet of the fresh airplenum module; operating the coil of the fan coil unit; and operatingthe fan of the fan coil unit; wherein the flow of conditioned airthrough the fan coil unit is provided by the pressure gradient generatedby the flow of outdoor air through the fresh air plenum module and theoperation of the fan.
 15. A method as claimed in claim 13, the methodcomprising operating the system in an eco mode, the eco mode comprising:providing outdoor air to the second inlet of the fresh air plenummodule; not operating the coil of the fan coil unit; and not operatingthe fan of the fan coil unit; wherein the pressure gradient generated bythe flow of outdoor air through the fresh air plenum module induces aflow of air through the fan coil unit.